Collateral host means:

Options

A. Additional host
B. Host in which life cycle is completed
C. Alternate host
D. Infected host

Answer

### Step-by-Step Solution:

1. **Understanding the Term "Collateral Host":**
- A collateral host is a type of host that is associated with a parasite.

2. **Relationship to Primary Host:**
- The collateral host belongs to the same family as the primary host. This means that both hosts are related in terms of their biological classification.

3. **Survival of Parasite:**
- The key characteristic of a collateral host is that it allows the parasite to survive in the absence of the primary host. This is particularly important during times when the primary host is not available, such as during off-seasons.

4. **Differentiating from Alternate Host:**
- It is essential to differentiate between a collateral host and an alternate host. An alternate host belongs to a different family than the primary host, while a collateral host remains within the same family.

5. **Conclusion:**
- Given the definition and characteristics of a collateral host, it can be concluded that it is essentially an "additional host" for the parasite.

6. **Final Answer:**
- Therefore, the correct answer to the question "Collateral host means:" is **Option A: additional host**.